The invention relates to a cooled two-part paiston.
Such a piston is known, for example, from DE 37 32 925 C1.
If an internal combustion engine having such a piston is now supposed to be used in an approximately horizontal installation position, in operation (e.g. below-floor engine, Boxer engine), there is the risk that cooling oil will collect in the lower region, on the cylinder wall, and get into the combustion chamber, going past the piston rings, particularly when the internal combustion engine is shut off and while it is standing. Aside from the undesirable oil consumption, this causes stronger smoke development (e.g. blue smoke) to occur when the internal combustion engine is started.
From the state of the art, reference with regard to smoke development when starting, in the case of an internal combustion engine having a cylinder arranged horizontally should also be made to DE 197 08 892 C1, in which it is proposed, in the case of a one-part piston not having liquid cooling, to form a labyrinth-like pressure equalization passage between the combustion chamber and the crank chamber, whereby the piston rings that face the combustion chamber are provided with recesses, in each instance, which connect the annular space between adjacent piston rings with the bottom of the ring groove, in each instance.
Furthermore, in the case of a horizontal internal combustion engine, a one-part piston without liquid cooling is known from JP 3-8640 U, which piston is provided with an axially running recess on the outside of its skirt, which recess is connected with a feed-back bore in the cylinder, to the crankcase chamber, in order to drain oil that has been stripped from the piston rings.